1. Field of the Invention
The invention relates to a method of manufacturing a multilayer plasterboard in which a core layer of the board has a different density from the outer layers, and to an apparatus therefor.
2. Description of Related Art
The manufacture of a multilayer gypsum plasterboard is disclosed in U.S. Pat. No. 2,940,505. This document discloses the application of thin layers of gypsum plaster slurry to two paper liners. A core layer of gypsum plaster slurry is applied to the first slurry coated liner, and the second slurry coated liner is brought onto the exposed surface of the core. A very satisfactory bond between the liners and the plaster is said to result, even without the use of starch or other adhesive. The apparatus disclosed in U.S. Pat. No. 2,940,505 includes three slurry mixers, supplying gypsum slurry to the two paper liners and the core respectively. In practice, this necessitates complex control systems to ensure synchronicity between the mixes and to ensure that each mixer supplies slurry at the correct rate. The capital and running costs of such an arrangement are high compared to a conventional plasterboard manufacturing line with only one mixer.